While the Iran hostage crisis and an oil embargo may have tarnished his presidential legacy, Jimmy Carter has passed retirement with flying colors, as his 2002 Nobel Peace Prize attests.

Passion is one of the keys to sustained fulfillment during retirement, and President Carter's pursuit of humanitarian issues is not only noble, it demonstrates his deep devotion for something he identified early on as meaningful and worth pursuing. He has been doing good deeds with such vigor from virtually the moment he left office,

Struggling with no-easy-fix, macro issues like the Israeli-Palestinian conflict, homelessness, genocide and world hunger has kept him mentally engaged, which is vital to post-career satisfaction. And the former president clearly understands the key retirement value of keeping up with (and adding to) a social network built during career, as his advocacy with today's world leaders demonstrates.

That he founded The Carter Center jointly with his wife, Rosalynn, soon after leaving office suggests they planned their post-White House years together. That bespeaks the best kind of retirement planning: taking into account the wants and needs of those closest to you.

Most former presidents take pen in hand upon leaving office, but Carter has done it a little differently. There are his memoirs, his musings on politics, his deep explorations of the Middle East conflict, and then there is The Hornet's Nest, a work of fiction set in the south during the Revolutionary War. There's a good chance he wrote it to please one person: himself. In retirement, that is not only permissible, it's healthy.